Effects of acute normovolemic haemodilution on cardiorespiratory changes in hyperthermia and its physical treatment

Brozmanova, A; Žila, Ivan; Javorka, K; Porubcan, J; Kapsova, J

doi:10.1080/02656730410001714968

Cited by 3 publications

(2 citation statements)

References 32 publications

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“…Our experiments did not reach the heat stroke condition and did not increase the rabbit temperature more than 43°C. There was no need to measure blood gas tension or pH in this study, since Brozmanova et al (2004) proved they do not change signiWcantly during hyperthermia nor do they aVect cerebral perfusion.…”

Section: Discussionmentioning

confidence: 94%

Influence of hyperthermia on carotid blood flow using 99mTc-HMPAO

2007

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Hyperthermia can be the result of many causes such as environmental conditions, brain tumors and infectious diseases. Since hyperthermia is very common, its role in causing stroke through a decrease in cerebral blood flow needed further emphasis. The aim of this study was to record cerebral blood flow in vitro by using isolated rabbit carotid artery strips and in-vivo using radioactive isotope scanning during temperature elevation. The recording of isometric tension in rabbit carotid artery strips in organ baths, and the scintigraphic cerebral imaging of technetium-99m-hexamethyl-propyleneamineoxime (99mTc-HMPAO) using Gamma camera, were acquired at control and higher body temperature by 4 degrees C. Blood pressure was measured through femoral artery and cerebral blood flow was measured through carotid artery. Elevating temperature by 4 degrees C induced reproducible contraction. During hyperthermia, the carotid artery contraction leads to a decrease in cerebral blood flow although the blood pressure did not decrease. The uptake of 99mTc-HMPAO in the brain was significantly reduced. This decrease in cerebral perfusion is regionally dependent, which is more in the frontal area, the cerebral hemispheres than the cerebellum. The decrease was 36+/-3, 37+/-2, 22+/-2%, respectively. Hyperthermia causes carotid artery contraction leading to decrease in cerebral blood flow, which was confirmed by 99mTc-HMPAO images. The decrease is regionally dependent. Since the blood pressure did not decrease by heating, the reduction in cerebral perfusion is mainly due to carotid contraction. The applied neck cooling may be considered as a promising therapeutic strategy for the hyperthermic patient to avoid brain damage. This can be achieved by external application of an ice-water-perfused neck collar.

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Section: Discussionmentioning

confidence: 94%

Influence of hyperthermia on carotid blood flow using 99mTc-HMPAO

2007

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“…Since the transient decrease of GFR and renal plasma flow reported by Kanter [3] occurred in dogs exposed to an air temperature of 49°C for 3–4 h, a concern on an effect of such a condition in a human referred for radionuclide renography is warranted. Brozmanova et al [15] showed that blood gas tension and pH did not change significantly during hyperthermia, therefore they have no effects on kidney function. Accordingly, the objective of our study was to look at the possible effects of hyperthermia on the scintigraphic pattern of renography on an animal model.…”

Section: Discussionmentioning

confidence: 99%

Hyperthermia Alters Kidney Function and Renal Scintigraphy

et al. 2007

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Background/Aim: Fever can be caused by different reasons such as environmental conditions, acute rejection after kidney transplantation and bacterial diseases including kidney and urinary tract infections. The present study represents a novel idea of investigating the direct effect of body temperature elevation on kidney function to determine whether hyperthermia alters the kidney function transiently leading to inaccurate findings and possible misinterpretation of the radionuclide (^99mTc-MAG-3) renography studies. Methods: Renography studies were performed on New Zealand White rabbits weighing approximately 3–3.5 kg. Each rabbit was inject with 48.1 MBq (1.3 mCi) technetium-99m-mercaptoacetyltriglycine (^99mTc-MAG-3). Studies were acquired using a gamma camera equipped with a low-energy, high-resolution collimator interfaced with a computer. Dynamic images were acquired as 2-s frames for the first 1 min and every 30 s for the next 30 min on a matrix of 64 × 64. Regions of interest were drawn over the whole kidneys. Radioactivity time curves were generated from the regions of interest. Time to peak activity (T_max), time from peak to 50% activity (T_½), and the uptake slope of each kidney were calculated from the renograms. Three days later the same protocol was repeated for the same rabbit but with a higher body temperature by 2°C. Then it was repeated with a higher body temperature by 3°C, then 4°C with the same interval period. Blood pressure was measured using a catheter inserted into the femoral artery connected to a Lectromid recorder at normal temperature and during increasing the temperature by 2, 3 and 4°C. Renal blood flow was also measured via the renal artery using an electromagnetic blood flow sensor connected to a flowmeter. Creatinine and blood urea nitrogen (BUN) in blood were measured in control and hyperthermic rabbits. Results: During hyperthermia the experimental curves shifted to the right of the control curves indicating that there was a delayed renal uptake of ^99mTc-MAG-3 and clearance of radioactivity. This delay was proportional to body temperature. Calculated averages were: T_max 1.6 ± 0.1, 2.8 ± 0.3, 8.8 ± 1, 15 ± 4 min; T_½ 2.77 ± 0.2, 3 ± 0.4, 8.9 ± 1.1, 20 ± 3.4 min, and perfusion index 190 ± 5, 201 ± 4, 218 ± 7, 224 ± 9 of control and hyperthermic (elevation of temperature 2, 3, and 4°C) rabbits, respectively (n = 6; p < 0.05). Mean arterial pressure and renal blood flow did not significantly change during hyperthermia. Creatinine and BUN were proportionally elevated to high temperature. Conclusions: Our results indicate that hyperthermia causes a transient alteration in the function of the kidney and scintigraphic pattern on radionuclide renography. Radionuclide renography studies may be performed at normothermic temperature since interpretation at higher body temperature could lead to misleading results, and temperature should be checked and recorded for single and follow-up radionuclide renography studies.

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Effects of diuretic-induced hypovolemia/isosmotic dehydration on cardiorespiratory responses to hyperthermia and its physical treatment in rabbits

Brozmanova

Jochem

Javorka

et al. 2006

International Journal of Hyperthermia

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Under conditions of heat stress and hyperosmotic dehydration, both animals and humans reduce thermoregulatory evaporation and regulate deep body temperature at elevated levels. Regarding the mechanisms, the main role in producing these thermoregulatory changes during dehydration is attributed to the increased osmolality of body fluids, although the role of the decreased plasma volume without changes in plasma osmolality (hypovolemia/isosmotic dehydration) has not been so far investigated. There are also controversial experimental results regarding the effects of dehydration on heat stress-induced cutaneous vasodilation. Therefore, this paper studied the effects of hypovolemia/isosmotic dehydration on cardiorespiratory responses to hyperthermia and its physical treatment in 17 anaesthetized adult rabbits. The animals were divided into two groups: normovolemic group (NV; n = 10) and hypovolemic group (HV; n = 7). In the HV group, hypovolemia/isosmotic dehydration (decrease in plasma volume by 16.1 +/- 1.2%) was induced by furosemide (5 mg kg-1 i.v.) without change in measured plasma Na+ concentration. Hyperthermia (the rise in body temperature (BT) to 42 degrees C by a gradual body surface heating) caused significant increase in minute ventilation (VE) in both groups. However, VE values were significantly higher in the HV rabbits compared to the NV animals despite the lower breathing frequency (p < 0.05). The panting was absent in the HV rabbits at the BT of 42 degrees C, unlike the NV animals. From cardiovascular variables, the vasoconstrictor response in visceral (mesenteric) region during hyperthermia in hypovolemic/isosmotic animals was attenuated (p < 0.05), whereas the heat stress-induced cutaneous vasodilation was not influenced by hypovolemia. Recovery of the BT by body surface cooling was accompanied by further increase in VE in the NV group, whereas VE decreased (p < 0.05) in the HV animals. Cooling led to recovery of the cardiovascular parameters. There were found no significant cardiorespiratory differences between the groups (NV:HV) during cooling. The lower frequency of breathing and attenuation of the mesenteric vasoconstriction during exogenous hyperthermia are present not only during hyperosmotic dehydration induced by water deprivation, but they also occur under conditions of furosemide-induced isosmotic dehydration/hypovolemia in rabbits. The heat stress-induced cutaneous vasodilation regarding its biological importance was not influenced by hypovolemia/isosmotic dehydration. Therefore, it is suggested that hypovolemia alone is sufficient to produce described respiratory, thermoregulatory and cardiovascular changes in dehydrated rabbits during exogenous hyperthermia, whereas hyperosmolality is not a requisite.

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Effects of acute normovolemic haemodilution on cardiorespiratory changes in hyperthermia and its physical treatment

Cited by 3 publications

References 32 publications

Influence of hyperthermia on carotid blood flow using 99mTc-HMPAO

Influence of hyperthermia on carotid blood flow using 99mTc-HMPAO

Hyperthermia Alters Kidney Function and Renal Scintigraphy

Effects of diuretic-induced hypovolemia/isosmotic dehydration on cardiorespiratory responses to hyperthermia and its physical treatment in rabbits

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